Elastically suspended test bench for testing vehicle engines



Oct. 5, 1937 K. LURE NBAUM 0 ,1

ELASTICALLY SUSPENDED TEST BENCH FOR TESTING VEHICLE ENGINES Q Filed April 20, 1955 '2 Sheets-Sheet 1 fizz/912501.-

KARL Lu RENBAUM Affomdiy I 1 O t, 5,1937. K. LURENBAU M 2,095,142 ELASTICAZIJQYI SUSPENDED TEST BENCH FOR TESTING VEHICLE ENGINES Fiied April 20.1955 2 2 Sheets-Sheet 2 jiwejzzor: KARL LURENBAUM maimed-s,1937," Y I 2,095,142 3 UNITED STATES PATENT OFFICE ELASTICALLY SUSPENDED TEST BENCH FOR TESTING VEHICLE ENGINES Karl Liirenlminn, Berlin-Adlershof, Germany Application April 20,1935, Serial No. 11,395 In Germany April 17, 1934 15 Claims. (01'. 265-24) This invention relates to an elastically susincalculable additional stresses appear in the mapended test benchfor testing" vehicle= engines, terial and frequently lead tobreakage of the casparticularly. aircraft engines, and consists sub- 1 ing, although the engines themselves would have stantially in providing an engine bearerelasticab endured withouttrouble in normal operation.

ly supported relative to the foundation, .whose The invention overcomes these drawbacks and 5 mass and moments of inertia around the'three is illustrated, by way of example, in the accom- H principalaxes are equal to the mass and mopanying drawings, in which Figure 1 is a side ments of inertia of the wing cellule with the view of the test bench; Fig. 2, a transverse view i fuselage of the aeroplane or 'can be adapted by thereof Fig.3, a diagram of the measuring delo adjustable weights to the masses and moments vice; and Figs. 4 and5 are, respectively, a side of inertiazof diflerent types of aircraft and veand transverse view of another type of cushionhicles, and in arranging the-enginebearer proper ing.

in a central bearing flexible on all sides and sup- Referring to the drawings,l is the firm foun ,1 portingit by springs relative to the firm foundadation of the test bench, in which a heavy drum 1 tion, so .that the engine bearer is capable of 2 is arranged in aroller bearing 3. The outer 15 carrying out .free rotary oscillationsin three ririg of the roller bearing 3, by means of the planes and circular oscillations with the elastic elastic ring 4, is inserted in the foundation l central bearing as center, and that small parallel i so as to be flexible on all sides. At the front end,

displacements inthe three axial directions are thedrum 2 is supportedin vertical and horizontal possible, the frequencies of the natural oscilladirections relative to the foundation l by means 20 tions in the three principaldirections being beof the springs 5 and 6. The hand wheels 1 per low the low frequency of excitation developing in ,mit to readjust axis 3-3: of the bench, when i l idling. The engine is secured to the bearerin springs S are compressedunder the load of the,

- a manner correspondingto the natural elasticity machine to be tested and/or of additional weights ofthe installation, possibly by using the-installaapplied to the bench in order to adapt it to the tion itself, Further features ofthe invention will mass and moments of inertia of a certain airbedisclosed in the specification below. craft or vehicle. The adjustable stops 8 and 9 It is known in connection with testing work secure the construction against damage at too rigidly to secure vehicle enginestoi testibench great strokes, and the damping mechanism l6 1 frames arranged rigidly or"elastica.lly on the serves for reducing the shock-like impulses ap- 30 foundation" In view of the actual spring suspearing during irregular operation to a tolerable pension of the enginesin cushioned vehicles or degree. I freely floating airplanes, both method of attach- The engine I2 is secured to the exchangeable U .ment have provided to be unsuitable, since the fixing plate by means of a standard installatest data thusobtained do not permit conclusions tion III or a corresponding cushioning means. 35

as to how the engines will actually behavein A brake I5 is connected with the engine H by practical operation. The forces and moments means of a shaft l3 and two adjustable cou of inertiadue to the driving-gear produce shakplings l4. v 1 ing. oscillations of the engine, which, if the lat,-

In this way, the six possible degrees of freedom ter is, elastically secured, are partially compenin practical flying work, that means the freedom 40 sated within the engine as torsional andbending ofthe craft-to perform rotary movements about oscillations and partially transmittedto the cushthe three principal axes :r, y and z, and transioned vehicle or freelyfioatin'g aeroplane. In the latory movements in the direction of the axes known kinds of suspension in an elastic installav x, 1/ andz are reduced to the three essential ones,

1 '45tion in case of aeroplanes or, in motor vehicles, the forcesand moments of inertia appearing in in the manner of the two or, three point suspenthe three planes causing rotary oscillations of the sion stresses due tooscillation are knownv to redrum! about the elastic central bearingt, a. In main within the elastic limits of the material Figs. 1 and 2 respectively the three planes are and do not injuriouslyafl'ect the engine. Inth s indicated by the three axes It, 1/, z. The elastic I respect, rigid attachment of the engine, even; on arrangement of the central bearing 3, 4 permits a spring test bench, is open to the objection that it the adjustment in the direction a: at greater the oscillations of the engine are not;compendeflections, i i sated anymore as elastic deformations of .the- In the construction of the bearing 3, 4 shown,

, casing or as shaking oscillations ,ofthe entire the 1-2 plane is distinguished by the fact that 5 engine in elastic suspension with the result that at rotation about the axis a: the cushioning 0f t e elastic ring 4 does not act. The torque appearing in this plane causes twisting of the test bench, which by means of a ball bearing can adjust itself without friction, so that the amount of twist may serve as measure of the engine output.

An indicating device such as pointer l'l opposite a fixed scale l8, as illustrated in Fig. 3 may be connected with the drum 2 by any suitable means to follow angular movements of the drum about the axis :r-r. A cord-and-pulley drive may be used, for this purpose, one pulley 30 being rigidly connected to drum 2, and another pulley 3! to pointer l1, and the cord 32 being attached to both pulleys. Thus, on an angular movement of the drum in response to the torque, the pointer rotates likewise about point for instance from its original position ab to the position a-b, so that the torque may be read directly on the scale l8 if the latter is gauged accordingly.

According to the type of cushioning shown in Figs. 4 and 5, the weight and the torque are taken up by separate sets of springs, the spring l9 taking up the weight of the drum 2 and the springs 20 serving for taking up the torque. The tension of springs 20 may be adjusted by means of hand wheels 25, and the position of drum 2 by means of screw 21 supporting spring I9, and by means of hand wheels 26 cooperating with springs 24. By means of the radially adjustable weights 2| adapted to slide on the rods 22, 23 the moment of inertia around the axis a: can be varied. By making use of additional weights the mass of the drum 2 may be varied. The springs 24 take up shocks in horizontal direction. If the cushioning is dimensioned so that the natural frequencies of the rotary oscillations in the three axial directions lie below the lowest frequency of excitation during idling of the engines to be tested, the impulses due to the forces and moments of inertia of the engine will be taken up in an extraordinarily soft manner without any danger of resonance phenomena.

The mass and the moments of inertia of the drum 2 about the three principal axes of oscillation are preferably chosen as large as the mass and moments of inertia of the aeroplane cell con cerned. Variations in the moments of inertia can be easily effected in the manner described, and the actual conditions of practical flying can thus be imitated with respect to any engine on the test bench to an almost perfect degree.

The advantages afforded by the invention consist substantially in eliminating the difficulties connected with the operation of spring test benches. These difficulties are chiefly due to the fact that the six degrees of freedom possible in practical flying cannot be realized very well on a test bench without endangering safety in operation with respect to the coupling with the usual braking means, such as hydraulic or electrical brakes, etc. On the other hand, if the cushioning and the mass of the test bench are improperly dimensioned. undesirable resonance phenomena will appear and render practical operation impossible. For this reason, the invention reduces the six degrees of freedom of the flying aeroplane to the three essential ones, so that approximately the same conditions as prevail in practical flying are reproduced without lowering the safety in operation. Furthermore, by reducing the number of normally available degrees of freedom to three the design becomes extraordinarily clear. Oscillations can be readily coped with, so that the work can be done as in a rigid test bench with, normal brakes. Owing to the universally elastic arrangement, no additional stresses as the result of shaking oscillations can affect the engine which thus cannot be damaged. By equalizing the mass and moments of inertia of the test bench and the corresponding values of the aeroplane cell actual flying conditions are closely imitated. The spring suspension also brings it about that the shaking oscillations coming from the engine cannot be transmitted to the foundation and thus to the ground. The test bench according to the invention is particularly suited for being erected on light foundations without causing the least trouble.

I claim:

1. A test bench for engines of vehicles particularly of aeroplanes, comprising a substantially heavy bearer, means attached to said bearer for securing an engine thereto, and means for yieldingly supporting said bearer, adapted to permit limited movements of said bearer in all directions, the mass and the moments of inertia about the three principal axes of said bearer and said attached means being so dimensioned, that their natural frequencies in all directions are below those of the idling speed of the engine to be tested.

2. A test bench for engines of vehicles particularly of aeroplanes, comprising a substantially heavy bearer, means attached to said bearer for securing an engine thereto, means for yieldingly supporting said bearer adapted to permit limited movements of said bearer in all directions, and adjustable weights on said bearer, adapted to alter the mass and moments of inertia about the three principal axes of said bearer and said attached means whereby said mass and said moments of inertia may be made equal to those of the cellule and fuselage of an aeroplane for which the engine to be tested is destined.

3. A test bench for engines of vehicles particularly of aeroplanes, comprising a substantially heavy bearer, means attached to said bearer for securing an engine thereto, means for yieldingly supporting said bearer, adapted to permit limited movements of said bearer in all directions, the mass and the moments of inertia about the three principal axes of said bearer and said attached means being so dimensioned, that their natural frequencies-in all directions are below those of the idling speed of the engine to be tested, and adjustable weights in connection with said bearer, adapted to alter the mass and moments of inertia about the three principal axes of said bearer and said attached means, whereby said mass and said moments of inertia may be made equal to those of the cellule and fuselage of an aeroplane for which the engine to be tested is destined.

4. A test bench for engines of vehicles particularly of aeroplanes comprising a frame, a substantially heavy bearer having an axis of torque, means attached to said bearer for securing an engine thereto, a bearing for said bearer near, one of its ends, adapted to permit free angular movements of the bearer with respect to its axis of torque, yielding means attached to said frame for holding said bearing, adapted to permit limited movements of said bearing in all directions, and resilient means for supporting said bearer at a distance from said bearing, adapted to permit limited movements of said bearer in a plane at right angles to the axis of said bearing, whereby the bearer is permitted to perform free rotary oscillations in three planes at right angles to each other, and circular oscillations with the center of said bearing as thecenter of the oscillations, andfto perform small translatory movements in the ver- 3 tical, sideways and lengthwise directions; 7

I A test bench for, engines of vehicles particu;

1 larlyof aeroplanes comprising a frame, a substan-- .tially heavy bearer having'an axis-"of torque, means attached to said bearer for securing an en-f gine thereto, ajbearing for saidbearer near, one

of its' ends, adapted to permit free angular move ments of the bearenwith respect toitsaxis of torque yieldingmeans attached to said frame for holding said bearing; adapted to permit limited movements of said'bearing inyall directions, and resilient means for supporting said bearer at. a distance from said bearing, adapted to permit limited movements of said bearer in a plane at i right angles to the axis of said bearing, whereby the bearer is permittedtoperform free rotary 'oscillations in three planes at-right angles to each other, and, circular oscillations with the center of said bearing as the center of the oscillations,

1 and to perform small translatory movements in tance from said bearing, adapted to permit limited movements of said bearer in a plane at right anthe vertical, sideways and lengthwise directions,

the mass and moments of inertia about the three principal axes of said bearer and said engine securing means being so dimensioned, that their natural frequencies in all directions are below the idling speed of an engine to be tested on the bench. i i

i 6. A test bench for engines of vehicles particularly of aeroplanes comprising a frame, a sub-. stantially heavy bearer having an axis of torque, means attached to said bearer for securing an ent i ginethereto, a bearing for said bearer near one of its ends, adapted to permit free angular movements of the bearer with respect to its axis of torque, yielding means attached to said frame for holding said bearing, adapted to permit limited movements of said bearing in all directions, resilient means for supporting said bearer at a disf gles to the axis of said bearing,- whereby the bearer is permitted to perform free rotary oscillations in three planes at right angles to each other, and

circular oscillations with the center of said bearing as the center of the oscillations, and to perform small translatory movements in the vertical, sideways and lengthwise directions, and adujustable weights in connection with saidbearer,

1 adapted to alter the mass and moments of inertia i said attached means, whereby said mass and moi ments of inertia may be made equal to those of about the three principal axes of said bearer and the cellule and fuselage of 'an aeroplane for which I the engine to be tested is destined.

'7. A test bench as claimed in claim 4 in which said means attached to the bearer for securing an engine thereto comprise cushioning means corresponding to those as used in the mounting of such engine in a vehicle. v

8. A test bench for engines of vehicles particu- "larly of aeroplanes comprising a frame, a bearer having an axis of torque, means attached to said bearer for securing an engine thereto, a bearing yieldingly attached to saidframe for supporting said bearer near one of its ends and adapted to permit said bearer to freely rotate about its axis of torque, springs in connection with said frame for supporting said bearer at a distance from said bearing and for counteracting a torque transmitted to said bearer, resilient means in connection with said frame for limiting lateral movei ments of said bearer, and indicating means in connection with said bearer for indicating angular movements ofsaid bearer as a measure of torque. H p 9. .A test bench for engines of vehiclesypare ticularly of aeroplanes comprising a frame, a substantially heavy bearer having a longitudinal axis, means attached to one end of said bearer for securing an engine thereto, a bearingior said bearer, near its other end, yieldingly mounted on said frame, and adapted to permit free oscillations of thjebearer about itslongitudinal axis, springs resting against said frame for supporting said bearer, laterally arranged springs engaging said bearer for counteractinga torque of said bearer, horizontally arranged springs .for checkinglateralmovements of said bearer, and means in" connection withqsaiddbearer forindicating,

angular movements of said bearer about its longitudinal axis as a measure for the torqueto which,

thebearer is subjected.

, 10.'A test bench for'engines of vehicles, particularly of aeroplanes comprising a frame, a

ient means between said frame and said bearer for supporting it and for counteracting torques of the bearer about its longitudinal axis, and

means in connection with said bearer for indicating torques;

11. A test bench for engines of vehicles, particularly of aeroplanes comprising a frame, a

' drum-shaped bearer, an exchangeable covering plate secured to one end of said drum, means attached to said covering plate for securing an engine thereto, a bearing for said bearer near its other endysaid hearing being yieldingly mounted on said frame, resilient means on said frame for supporting said bearer at a distance from said bearing and for counteracting torques transmitted tosaid bearer, resilient means on said frame for checking lateral movements of said bearer, and means in connection with said drum for indicating its angular movements about its longitudinal axis.

12. A test bench for engines of vehicles particularly aeroplanes comprising a frame, a substantially heavy bearer having a longitudinal axis, means attached to one end of the bearer for securing an engine thereto, a bearing for said bearer near its other end, said bearing being yieldingly mounted on said frame and adapted to permit free pscillations of the bearer about its longitudinal axis, springs mounted on said frame laterally of the longitudinal axis of the bearer for supporting said bearer and counteracting a torque transmitted thereto, horizontally arranged springs for checking lateral movements of said bearer, and adjustable weights in connection with said bearer, adapted to alter the mass and the moments of inertia about the longitudinal axis and about axes at right angles thereto, of said bearer and said attached means.

13. A test bench for engines of vehicles particularly of aeroplanes comprising a frame, a substantially heavy bearer having a longitudinal axis, means attached to one end of said bearer for securing an engine thereto, a bearing for said bearer near its other end, said bearing being yieldingly mounted on said frame and adapted to permit free oscillations of said bearer about its longitudinal axis, springs mounted on said frame laterally of the longitudinal axis of said bearer and at a distance from said bearing for supporting said bearer and for counteracting a torque transmitted thereto, horizontally arranged springs on said frame for checking lateral movements of said bearer, individualmeans for adjusting each of said springs whereby the zero position of the bearer may be adjusted. 14. A test bench for engines of vehicles particularly of aeroplanes comprising a frame, a substantially heavy bearer having a longitudinal axis, means attached to one end of said bearer for securing an engine thereto, a bearing for said bearer near its other end, said'bearing being yieldingly mounted on said frame and adapted to permit free oscillations of said heater about its longitudinal axis, a spring on said frame for supporting said bearer at a distance from said bearing, a pair of springs mounted on said frame laterally of the longitudinal axis of said bearer and at a distance from said bearing for counteracting a torque transmitted thereto, horizontally arranged springs on said frame for checking lateral movements of said bearer, individual means for adjusting each 01' said springs whereby the zero position of the bearer may be adjusted.

15. A test bench as claimed in claim 11 further comprising dampening means interposed between said bearer and said frame for reducing shocklike impulses of the bearer.

KARL L'URENBAUM. 

